in this field, but cooperation between developed and less developed countries, and support by the United Nations, its specialized agencies, and other international organizations are needed to accelerate applied research and application, especially social and psychological research and development and testing of new contraceptive methods.
Welfare Policies Leading to Reduced Fertility. The decline in fertility in the Soviet Union, Europe, and North America that took place during the 19th and 20th centuries, and more recent declines in Japan and in some less developed countries, including Taiwan, South Korea, and Costa Rica, strongly indicate that married couples will limit the size of their families if they believe it is in their interest to do so and if means for controlling their own fertility are available to them. The parents' perception of their interest and their corresponding actions depend in part on social traditions and intuitive behavior patterns, as well as on conscious rationality.
Children provide both economic and psychic or social benefits to their parents and to other children in the family. During childhood and youth, they may contribute to family income by working with the family on a farm or in the production of handmade goods, or in a job outside the home. Those children who survive their parents can contribute to their parents' security in old age. Moreover, aside from these economic gains, it is part of our inheritance as human beings that most people like children and want to have some of their own. The psychic rewards of a family life enriched by children are reinforced by social norms, particularly in traditional societies with their extended or clan families and the many benefits conferred by kinship. In addition, the psychic and social costs of preventing births in a society without a high level of contraceptive technology are extraordinarily large, because they almost inevitably involve multiple induced abortions, late marriage, separation of the marriage partners over long periods, or some unsatisfactory modification of sexual relationships.
Children also produce costs, including the money costs of pregnancy and delivery, of feeding, clothing, housing, medical care, and education; the "opportunity cost" of the time and effort spent by parents to bring up their children (the magnitude of this cost depends upon the opportunities that exist for the parents to gain desired goals from other uses of the same time and effort); and the deprivation and health consequences to the mother and her children resulting from an additional child.
Both benefits and costs, as perceived by the parents, will vary with the number and sex of living children in the family. Probably most of the perceived benefits from an added child are highest when the number of children in the family is small. The incremental perceived benefits become less as the number of children increases. Some of the incremental costs of an added